1. Field of the Invention
The present invention relates to a high vacuum hot press for heating and pressing a multi-layer workpiece including boards such as, for example, printed wiring boards, ceramic boards and covered boards, and an adhesive, so as to produce a multi-layer board, such as a multi-layer printed wiring board and, more particularly, to a high vacuum hot press which is suitable for fabricating multi-layer boards in a relatively short time and at a high accuracy.
2. Prior Art
In the fabrication of high density multi-layer boards by hot presses, a higher finishing accuracy and warp and twist resistance have been required for the boards. To meet and satisfy this requirement, a typical attempt is disclosed in Japanese Laid-Open Patent Publication 62-156931 in which a pair of hot plates heat a multi-layer workpiece, whereas, a pair of bolsters press the workpiece through the respective hot plates. A heat insulating material is interposed between each pair of the hot plates and the corresponding bolster for uniform heating of the workpiece to remove thermal strains therefrom.